1. Field of the Invention
This invention relates to a sustained-release composition comprising a physiologically active protein drug, a hyaluronic acid or salts thereof, a polyalkyl oxide, and an amino acid. The composition allows a persistent release of the physiologically active drug for an extended period of time, preferably for one week or longer.
2. Description of the Related Art It has been reported that protein drugs are useful for treating various disease because they have a high physiological activity in the living body and a high specificity to a target. It is also reported that protein drugs have a short half-life and a low absorption rate in the living body, which limit the availability of protein drugs as a treatment drug. Protein drugs are usually administered to a patient via injection routes. The injection of protein drugs into the patient is usually painful. The half life of the injected protein drugs in the patient is generally 2-4 hours and the patients are required to be administered with the drugs everyday or every other day for an extended period of time, for example, one year or longer.
Sustained release formulations of protein drugs were proposed. During the early stage of the development of sustained release formulations of a protein drug, liposomes, microcapsules, and implants containing the drug have been suggested. However, these formulations were not satisfactory because the protein contained in the formulations easily lost its activity and they failed to produce a sustained release of the drug. Polymer microparticles containing a protein drug have been proposed. The microparticles formed from a non-biodegradable polymer have problems that they are not digested in the patient's body, and thus sometimes, an operation to remove the unsolved residues was needed. They are also harmful to the living body and the control of the release of the drug is difficult.
In order to overcome the drawbacks related with the use of a non-biodegradable polymer, microparticles in which a drug is entrapped into the biodegradable polymer have been suggested. The biodegradable polymer of the microparticles is slowly degraded in patient's body and the drug is released. As biodegradable and biocompatible polymers, synthetic polyesters such as polylactides, polyglycolides, poly(lactide-co-glycolide) (PLGA), polyanhydrides, polyorthoesters, polyphosphazenes, pseudopolyaminoacids have been employed. Microcapsules made from polyesters such as PLGA produce a sustained release of a peptide drug for an extended period of time ranging from one week to one month. However, the use of the PLGA in producing sustained release formulations of protein drug was limited because the hydrophobic property of the PLGA caused the degeneration of protein drugs, which destroys the physiological activity of the drug. The degradation of the PLGA itself in the patient body, which generates an acid and thus reduces the pH of the microparticles, also accelerates the degeneration and aggregation of the protein drug. The use of organic solvents, which are commonly employed in the production of microparticles using hydrophobic polymers, also causes unstabilization of the protein drug. The relatively slow digestion of the polymer in the patient also causes a feeling of a foreign substance.
A use of sustained release formulations made from a natural polymer has been proposed. Natural polymers such as gelatin, collagen, chitosan, carboxymethyl cellulose, alginate, or hyaluronic acids form a viscous gel upon absorbing water. The gel of the natural polymer produces a sustained release of a drug, including a protein drug. However, the gel easily loses its ability to retain the drug, when introduced into a patient body because the viscosity and density of the gel fast decreased in the patient body due to the digestion of the polymer and the dilution of gel inside the body. Thus, the natural polymer gel does not provide a satisfactory sustained release.
Hyaluronic acid is a natural, biodegradable, high molecular polymer made of N-acetyl-D-glucosamine and D-glucuronic acid. It is found in various organs and tissues in the living body. It is used in eye operations and rheumatisms treatments. There have been attempts to use hyaluronic acid gels in sustained release formulations. Generally, the higher the viscosity of the hyaluronic acid gel, the more effective in producing the sustained release of a protein drug. However, a composition containing several % of the hyaluronic acid gel is too viscous and difficult to be introduced into a patient by an injection.
Like other natural polymer gel formulations, hyaluronic acid gel formulation of a protein drug does not provide an effective sustained release of the drug once it is introduced into a subject. For example, when an insulin formulation comprising 1% hyaluronic acid gel, as disclosed in JP 1989-287041, was injected to a rabbit, the glucose blood level lowering effect lasted not more than 24 hours after the injection. U.S. Pat. No. 5,416,071 describes a sustained release formulation of interferon comprising 1.5% hyaluronic acid and plasma protein. When the formulation of interferon was introduced into a subject, the blood level of interferon sharply decreased to 1/10 of its initial level, within 24 hours after the injection.
As an alternative to gel formulations, microparticles comprising a protein drug and a hyaluronic acid or its salts, which are produced by spray drying, have been proposed. For example, U.S. Application Publication No. 2003/0064105 describes a sustained release formulation which was prepared by producing hyaluronic acid microparticles comprising a protein drug using spray drying; coating the microparticles with a lipophilic material such as lecithin, and dispersing the coated microparticles into an oil. It also describes that the coated microparticles are formulated into an oil-in-water emulsion. When an oil-in-water emulsion of the lecithin-coated microparticles of interferon-alpha was injected to a rabbit, the blood level of the interferon-alpha was maintained for an extended period of time.
To eliminate the coating process mentioned above, a lipophilic material can be dispersed in a solution containing a hyaluronic acid and an active ingredient and the resulting solution is subject to drying (e.g., spray drying). U.S. Application Publication No. 2003/0064105. For a practical viewpoint of commercialization, the solubilization of the lipophilic material is cumbersome as well as the quantization of the drug content and the analysis of the microparticles are difficult.
U.S. Pat. No. 6,375,988 discloses a drug composition with a controlled drug release rate. The drug composition comprises: a matrix formed of (a) a biodegradable, biocompatible high-molecular substance and/or polyvalent metal ions or polyvalent metal ion source, and (b) hyaluronic acid or a salt thereof, and a drug incorporated as an ingredient (c) in the matrix. The component (a) includes gelatin, sodium casein, albumin, lysozyme chloride, poly-L-lysine, chitosan, Ca2+, Al3+, and Fe3+. The drug covers a broad spectrum from anti-inflammatory drugs to arthritis therapeutics. The hyaluronic acid or its salts have a molecular weight ranging from 600,000 to 2,000,000 Da, especially from 1,000,000 to 2,000,000 Da. It does not specifically teach a controlled delivery of protein drugs. U.S. Pat. No. 6,375,988 does not teach a sustained release composition comprising a carrier substrate essentially consisting of a hyaluronic acid or its salts, an amino acid and a polyalkylene oxide and a protein drug incorporated in the carrier substrate, wherein a ratio of a molecular weight (Da) of the protein drug to a molecular weight (Da) of the polyalkylene oxide is about 1:0.5-1:10.
In conclusion, there still is a need for a sustained release formulation of a protein drug, which shows an excellent sustained release of the drug for an extended period of time while retaining the physiological activity of the drug.
Polyethylene glycol (PEG) is one type of polyalkyl oxides. Low molecular weight PEGs (molecular weight of less than 1000 Da) are liquid at the room temperature, while high molecular weight PEGs (molecular weight of 1000 Da or more) are solid. High molecular weight PEGs have been used as a plasticizer, a suppository base, and a hydrophilic excipient. Handbook of Pharmaceutical Excipients, 2nd Ed., The Pharmaceutical Press (1994). Low molecular weight PEGs have mainly been used as a solvent or a vehicle for drug compositions. Low molecular weight PEGs have been used as a stabilizer to prevent crystallization or precipitation of protein drugs in liquid formulations of the protein drugs. International Journal of Pharmaceutics, 185, 129-188 (1999).
Low molecular weight PEGs in a liquid form were proposed to be used as a vehicle for a solid formulation of proteins. For example, U.S. Pat. No. 5,385,738 describes a method in which proteins such as IGF-1 or B-hGH mixed with collagen are freeze-dried and pulverized to give powders, which are then dispersed in the liquid PEG. U.S. Pat. No. 6,004,549 describes a use of PEGs as a vehicle of crystalline interferons. According to U.S. Pat. No. 6,004,549, mixtures of PEGs of different molecular weights are proposed. For example, it describes the use of the mixture of PEG 3350 and PEG 400 or PEG 40,000 and PEG 550 in the production of an injectable sustained release composition of crystalline interferons. Uses of the PEGs of molecular weight of 8000 Da or 3350 Da are also suggested. However, U.S. Pat. No. 6,004,549 does not teach or disclose a sustained release composition comprising a carrier substrate which consists essentially of a hyaluronic acid or its salts, an amino acid and a polyalkylene oxide and a protein drug incorporated in the carrier substrate, wherein a ratio of a molecular weight (Da) of the protein drug to a molecular weight (Da) of the polyalkylene oxide is about 1:0.5-1:10. The sustained release composition of interferon-alpha taught by U.S. Pat. No. 6,004,549 released interferon-alpha up to 48 hours after the injection.
It has been reported that drug compositions comprising low molecular PEGs as a vehicle produces a sustained release of a drug for a short period of time. For example, U.S. Pat. No. 4,041,155 describes a use of a solution of 80% PEG 400 or PEG 300 as a vehicle of somatostatin. A solution of somatostatin dispersed in a 38% PEG 400 solution showed a sustained release of somatostatin for 4 hours. U.S. Pat. No. 6,011,011 discloses a sustained release of protein drugs from a composition comprising PEG 300 or PEG 600. It was recommended to use less than 30% of PEG 300 because a high concentration of 40% by volume or more of PEG 300 may induce hemolytic effects around the injected site. Handbook of Pharmaceutical Excipients, 2nd, The Pharmaceutical Press (1994).